Goal: This revised application seeks funds to replace an existing scanning electron microscope (SEM with a state-of-the-art low vacuum scanning microscope/x-ray analysis system, the JSM-5600LV with a fully quantitative and advanced imaging X-Ray microanalysis system. Problem: The core of our present system is an Amray 1000a with a Kevex mu x 7000 Energy Dispersive X-ray Spectroscopy (EDS) system. Our SEM was manufactured in 1975. The Kevex mu x 7000 EDS is also of that vintage.While the instrument has provided many years of service, the system is out-dated and inadequate for current applications. In addition, parts are difficult if not impossible to obtain, so that a number of standard functions on our system are inoperable. Furthermore, the SEM does not have the capacity to produce or store digital information. The user group for this instrument has grown and requires significantly improved capabilities available on modem scanning electron microscopes, specifically higher magnification, digital images, variable energy ranges, as well as higher maximum energy, variable vacuum pressures, and x-ray analysis of individual environmental particles, including automated analysis for cell and metal studies. Significance: The instrumentation will serve an established and productive group of investigators performing NIH-sponsored research. Current use includes genetic/morphological comparisons, cell surface relationship among cell types following metal exposure, analysis of environmentally relevant particle composition, size and surface area. Scanning Electron Microscopy has become an indispensable analytical tool required to complete several of our funded studies. The instrumentation is part of a dedicated Bioimaging Core facility whose personnel, service and maintenance costs are supported by an NIEHS center grant and several program projects. There is growing demand for the use of the facility. Institutional support is demonstrated by past support of the facility, completed renovations, commitments for ongoing service contracts, and letters of commitment for future support.